What becomes of the BaSO4?
September 19, 2007 3:08 AM Subscribe
In the endothermic reaction where barium sulphate becomes aqueous barium and sulphate ions, what would adding barium chloride and (separately) sodium chloride do to the reaction? (and why?)
Response by poster: My apologies. When I asked "what would it do to the reaction?", I meant: which way would it shift the equilibrium point (and why?)
Yes, this is homework. (I've looked everywhere, not just being lazy)
posted by lazy robot at 5:20 AM on September 19, 2007
Yes, this is homework. (I've looked everywhere, not just being lazy)
posted by lazy robot at 5:20 AM on September 19, 2007
well. here's what i know.
BaCl2 dissolution is exothermic.
NaCl dissolution is endothermic.
BaSO4 ⇄ Ba2+ + SO42- takes energy to move to the right.
the equilibrium point is determined by the amount of available energy. dissolving some additional BaCl2 should evolve heat, which is more energy available to dissolve more of the sulfate salt.
presumably the NaCl behavior would be the opposite, driving the equilibrium back to the left. (though i think this depends on which has a larger positive heat of solution, the sodium chloride or the barium sulfate, and i dunno the sulfate number, but given that this is homework, i expect this is the answer that's being looked for.)
posted by sergeant sandwich at 5:51 AM on September 19, 2007
the equilibrium point is determined by the amount of available energy. dissolving some additional BaCl2 should evolve heat, which is more energy available to dissolve more of the sulfate salt.
presumably the NaCl behavior would be the opposite, driving the equilibrium back to the left. (though i think this depends on which has a larger positive heat of solution, the sodium chloride or the barium sulfate, and i dunno the sulfate number, but given that this is homework, i expect this is the answer that's being looked for.)
posted by sergeant sandwich at 5:51 AM on September 19, 2007
They're not really reactions, well not in my sense as an organic chemist. They merely are equilibria, and the addition of barium chloride will cause less of the barium sulfate to dissolve (except according to popular theory all sulfates are water soluble) due to the common ion effect upon dissolution. The addition of sodium chloride would cause less of the barium chloride to dissolve, via the same mechanism.
If you can be more specific I can probably be of more help.
posted by koolkat at 6:23 AM on September 19, 2007
If you can be more specific I can probably be of more help.
posted by koolkat at 6:23 AM on September 19, 2007
Common Ion effect.
Adding Barium chloride will shift the eq. to the left (towards BaSO4).
Adding Sodium Chloride will do nothing (no common ions).
When searching for chemistry stuff online, try to hunt for the ideas, not any one specific reaction.
posted by Orange Pamplemousse at 8:23 AM on September 19, 2007
Adding Barium chloride will shift the eq. to the left (towards BaSO4).
Adding Sodium Chloride will do nothing (no common ions).
When searching for chemistry stuff online, try to hunt for the ideas, not any one specific reaction.
posted by Orange Pamplemousse at 8:23 AM on September 19, 2007
Yes, this is homework. (I've looked everywhere, not just being lazy)
Have you tried asking the teacher? The point of the homework isn't to get the answer. It's to gain an understanding of the material. If you don't understand it well enough to complete the work, then it's probably more valuable letting the teacher know that so they can work with you on it.
posted by willnot at 10:02 AM on September 19, 2007
Have you tried asking the teacher? The point of the homework isn't to get the answer. It's to gain an understanding of the material. If you don't understand it well enough to complete the work, then it's probably more valuable letting the teacher know that so they can work with you on it.
posted by willnot at 10:02 AM on September 19, 2007
This thread is closed to new comments.
also, can you be more specific about what you mean by what "would it do to the reaction"?
i'm having a real hard time figuring out why adding BaCl or NaCl would do anything at all, except that they each have their own heats of solution, which would independently add or remove heat from the mixture.
i suppose if there were enough BaSO4 to saturate the solution, then adding BaCl might shift the equilibrium point and therefore change the temperature, but you didnt say anything about that. barring that, i really cant think of any reason why the two dissociation reactions wouldnt proceed largely independently.
posted by sergeant sandwich at 4:55 AM on September 19, 2007